Field of the Invention
The invention relates to a controller for the drive train of a motor vehicle (a drive train controller) having an engine and an automatic transmission.
As disclosed in German Patent DE 29 34 477 C3, conventional transmission and engine controllers vary the ignition angle to reduce engine torque with the aim of improving the ease of gear shifting and of reducing the stress on the transmission. In the case of engine and transmission controllers that are to be developed as new items, one prime necessity is to reduce pollution emissions. In order to do that, local improvements are being aimed for, that is to say an improvement in the engine system on one hand and in the transmission system on the other hand. However, since the two systems influence one another, such improvements result in limitations to the operation of the motor vehicle.
In the case of a known motor vehicle drive train according to U.S. Pat. No. 5,311,794, the cylinder of a lean-burn engine has a plurality of inlet valves, one of which (a swirl control valve) is open when the engine load is relatively high and is closed when the load is low. The air-fuel mixture ratio is higher when that valve is closed than when it is open. The fact that the valve is switched on or off for changing its position is a signal to the transmission controller, which suppresses any transmission shift process then and for a time interval after the change. Special engine operating conditions are not taken into account in the process.
A known motor vehicle according to German Published, Non-Prosecuted patent application DE 43 32 456 A1 has an engine with an exhaust catalytic converter, having an exhaust purity level that reduces with age. The automatic transmission in that motor vehicle has at least one economy shift program and one sport shift program, and it is provided with a device through which the transmission is automatically switched to the sport program at the start of the engine warming-up phase, in order to heat the catalytic converter more quickly. The transmission is automatically switched back to the economy program once the sport program has been switched on for a time that becomes longer as the total operating duration or total distance driven becomes greater.
A motor vehicle drive train having a Diesel engine and a transmission has a fuel controller which is dependent on the performance required by the driver. A plurality of families of characteristics contain empirically derived data relating to exhaust components and fuel consumption, according to Published European Patent Application EP 0 474 401 A2. The transmission controller uses the vehicle speed and the performance requirement together with an evaluation of the families of characteristics to determine which of those gear ratios that may be used for a permissible engine operating range is the "optimum". The optimum gear ratio is indicated. The optimization is carried out on the basis of low fuel consumption and the exhaust characteristics, and those criteria can be weighted in the process. That results in adaptive correction of the data in the fields of characteristics for the most useful engine operating range.